CVE-2023-22923Network attack vector

Authenticated service interruption via externally controlled format string

Published May 1, 2023 · Updated Jan 30, 2025

A format string flaw in Zyxel NBG-418N v2 firmware 1.00(AARP.13)C0 and earlier allows remote authenticated users to interrupt service. An undisclosed firmware binary uses attacker-controlled data as a format string, but Zyxel has not identified the binary or input-handling path. Valid device credentials and network reachability are required; WAN access is disabled by default, and the documented impact is service interruption only.

CVSS severity6.5
Medium
EPSS probability0.79%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A format string flaw in Zyxel NBG-418N v2 firmware 1.00(AARP.13)C0 and earlier allows remote authenticated users to interrupt service. An undisclosed firmware binary uses attacker-controlled data as a format string, but Zyxel has not identified the binary or input-handling path. Valid device credentials and network reachability are required; WAN access is disabled by default, and the documented impact is service interruption only.

The record

CVE
CVE-2023-22923
Published
May 1, 2023
Updated
Jan 30, 2025
Vendor
Zyxel Networks
Product
NBG-418N v2 firmware
Classifications
CWE-134, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 1, 2023CVE publishedPublication date reported by the CVE source.
  2. Jan 30, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< V1.00(AARP.14)C0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Zyxel Networks · NBG-418N v2 firmwareversion=< V1.00(AARP.14)C0

Published CVSS scores

6.5Zyxel CorporationCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-134Use of Externally-Controlled Format String
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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